In the related art, there have been known various inventions which control an operation of an electric tool and the like. For example, there is a configuration that a wireless communication is possible between the electric tool and a management device, and when both devices are separated to have a distance exceeding a certain value, the wireless communication becomes impossible, and a motor of the electric tool is switched into a rotation inhibition mode (Japanese Patent No. 5537106). In the relevant invention, when the electric tool is stolen by a third person to be moved to a place separated from the management device, the tool can become in an unserviceable state. Therefore, it is possible to prevent stealing.
There has been known a configuration that in an electric tool having a high stealing suppression effect, a person not wearing a proper authentication device cannot use the tool (Japanese Patent No. 4678199). Specifically, the electric tool includes an authentication circuit, and the authentication circuit performs an authentication using an identification code between the authentication circuit and the authentication device (wrist watch and the like) mounted on the wrist of the user. On the base of the authentication result, a permission is given with respect to the operation of the electric tool. In transmitting and receiving the identification code, the body of the user may be used as a transmission path, or RFID which is a short-range wireless communication may be used to transmit and receive a signal.
There has been known a configuration that in an invention using a table saw as an embodiment, it is intended that a contact of a human body with a rotating saw blade is prevented in advance (Japanese Patent No. 4429616). In the relevant invention, for example, the distance from a detection device to an object and the speed of the object approaching the detection device side (circular saw side) are detected by using a Doppler radar and the like, a case where the object approaches at a speed exceeding the speed presumed as an normal work operation is determined as an abnormal situation, and the circular saw is stopped before the object contacts the circular saw.
There is described an invention in which when the user has a head mounted display mounted thereon, and views the vicinity of the table saw, a camera of the head mounted display obtains an outside image, and the table saw is recognized to call attention to the user (JP 2014-120786 A).
As described above, for various purposes such as the stealing prevention and the danger avoidance, the operation of the tool is controlled based on the positional relation, the behavior, and the like, between the tool and the user.
The tool having electricity, air pressure, and other various kinds of power as an operation source generally has high output, and thus an erroneous use method causes a danger, and it is necessary to be cautious about handling. Since these are understood well by the user, a usual user performs the operation very carefully in the use of the tool. The careful operation is generally based on the premise that the user views the work area or the tool.
Various types of tools such as a nail driving machine, a circular saw, and an electric drill are used in various construction sites and work environments. In a case where such tools are operated with a use purpose, the work is carefully performed while the user has a care about an accident as described above. However, during a work, the user may perform another work at the same time with his eyes turned away from the tool. At this time, for example, the tool held by a hand is crushed into a wall to erroneously perform the operation, and thus the object is broken. When the tool is tangled in clothes, the operation may be performed erroneously, and the user may be hurt.